1. Field of the Invention
This invention relates to a hot water circulating system, and more particularly to a hot water circulating system for, for example, space heating which is adapted to supply hot water to a radiator by means of steam pressure without using a circulation pump.
2. Description of the Prior Art
A hot water circulating system which is adapted to carry out circulation of hot water heated in a water boiler to a radiator by steam pressure without using a circulation pump has been conventionally put in practice, as disclosed in Japanese Utility Model Publication No. 53929/1982, disclosure of which is incorporated herein by reference.
Such a conventional hot water circulating system is constructed in such a manner that steam pressure generated from a closed water boiler heated by a burner causes hot water in the water boiler to be forcibly fed through a radiator to an open tank arranged at a position above the water boiler, and water stored in the open tank is returned through an on-off valve to the water boiler.
In the conventional hot water circulating system constructed as described above, a structure for returning water in the open tank to the water boiler is the key to stable operation of the system. In general, a liquid level detector generates a signal for opening the valve while water remains in the water boiler, because when water is introduced from the open tank into the water boiler after hot water is fully emptied out of the water boiler, it is instantaneously vaporized to increase pressure in the water boiler to a level sufficient to prevent flowing of water from the open tank into the water boiler.
Unfortunately, when the valve is opened while water remains in the water boiler, a large amount of water vapor is discharged from the water boiler being heated through the valve to an ambient atmosphere, resulting in significant energy loss. Also, this leads to loss of water to be circulated and an increase in time required for each circulation cycle.
Thus, the conventional hot water circulating system results in the amount of water to be circulated in each circulating cycle being substantially reduced.
Accordingly, it would be highly desirable to develop a hot water circulating system which is capable of decreasing energy loss, preventing a decrease in hot water to be circulated and reducing time required for each circulating cycle.